(a+b+c)/3 = 29
(a+b)/2 = 22
(b+c)/2 = 39,50
(1) a+b+c = 29 x 3 <=> a+b+c = 87
(2) a+b = 22 x 2 <=> a+b = 44
(3) b+c = 39,50 x 2 <=> b+c = 79
Donc :
(2) a = 44-b
(3) c = 79-b
Tu remplaces dans la première équation :
44-b+b+79-b = 87 <=> 123-b = 87 <=> -b = 87-123
<=> b = -87+123 <=> b = 36
Ensuite :
a = 44-b, donc b = 36, donc a = 44-36 à savoir a=8
c = 79-b donc c = 79-36 donc c = 43
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